About 100 students at Downey High School were tested for tuberculosis by county health officials Wednesday, CBS News reported.Three students tested positive for tuberculosis late last year, according to CBS, which prompted the testing. Principal Tom Houts reportedly said one math class was tested Wednesday, along with the boys and girls volleyball teams. Test results are expected Friday, according to the report. Tuberculosis is a contagious and sometimes fatal bacterial infection that can be spread through coughing and sneezing. DUSD Superintendent Wendy Doty said the school district was contacting parents today with the following message: "First of all, Downey High School is open and operating as usual. The Los Angeles County Public Health Department recently notified Downey High School that two students tested positive for TB in the fall of 2011. On Wednesday, February 22nd, the Health Department screened approximately 100 students of the 4,200 students who attend Downey High. The results of that screening will be read on Friday, February 24th. At this point the Health Department feels that this situation is an isolated incident. We will continue to work with and take direction from the LA County Health Department and keep you informed of our next steps. Once again Downey High School is open and operating as normal. We will update you as more information is provided to us by the LA County Health Department."